src/HOL/Tools/ATP/atp_systems.ML

        "--mode casc -t " ^ string_of_int (to_secs 1 timeout) ^
        " --proof tptp --output_axiom_names on" ^
        (if is_vampire_at_least_1_8 () then
           (* Cf. p. 20 of http://www.complang.tuwien.ac.at/lkovacs/Cade23_Tutorial_Slides/Session2_Slides.pdf *)
           (if full_proof then
-             "--forced_options splitting=off:equality_proxy=off:general_splitting=off\
+             " --forced_options splitting=off:equality_proxy=off:general_splitting=off\
              \:inequality_splitting=0:naming=0"
            else
              "")
         else
           "") ^